Hello! I've been googling everywhere for a rockface type decoration that is also hollow. I finally came across one that would do but it is grossly expensive and a bit on the larger size since I will be putting it in my 6gal Fluval Edge.
"cichlid stones" look like rocks and you can stack them, but they are all hollow so they have tons of hiding places. I think they are awesome, but they are pricey. Search 'cichlid stones' or "ungerwater galleries". http://www.amazon.com/Original-Equip...776290&sr=8-16
I will use anything without regard to looks that I get cheap: skulls, mermaids, flower pots, faux logs and PVC.
You ought to be able to DIY faux rocks with something like fiberglass, use unsaturated polyester and a mold. To make them pretty, use model paint, then give everything a clear coat. But I lack any artistic skill.